Composite insulating material.



H. B. MAcFARLAND & R. J. SHOEMAKER- COMPOSITE INSULATING MATERIAL. APPLICATION FILED Nov.2s. m3.

1,139,395. Patented May 11, 1915.

lV/TNESSL'S: 1N VEQLTORJf I W K I l CLL%- 1 I" m/ HELON .B. MAoFARLAND, OF CHICAGO, ILLINOIS, AND ROBERT J. SHOEMAKER, 0F

TOPEKA, KANSAS; SAID SHOEMAKER ASSIGNOR TO SAID MAOFND.

COMPOSITE INSULATING MATERIAL.

Specification of Letters Patent.

Patented May 11, 1915.

To all whom it may concern Be it known that we, HELON B. MAO- FARLAND and ROBERT J SHOEMAKER, citizens of the United States, residing at Chicago, in the county of Cook and State of Illinois, and Topeka, in the county of Shawnee and State of Kansas, respectively, have invented certain new and useful Improvements in Composite Insulating Material, of which the following is a specification.

Our invention relates to the production of an insulating material suitable example, as a heat insulator for the walls of steel railway cars, refrigerator cars, cold storage plants, ice houses, or in other analogous situations, which will have very great insulating capacity, will not decompose or deteriorate under the influence of heat or dampness, will have considerable flexibility and also great tensile strength, and which can be inexpensively produced.

More specifically, the object of the invention is to provide a heat insulating material in the form of a composite board or sheet consisting of a stratum of felt-like fibrous cellulose, derived from certain plants by methods which will be hereinafter described, faced on one or both sides by a substance of denser, more tenacious character that may be produced from the fibers of the same plant. We prefer to use as raw material certain marine plants, particularly the plant known as Zostera marina of the family of Naiadacecc, commonly called eel grass. This plant, when treated according to the methods which we have devised, gives a very excellent heat insulating material. It has the advantage also of being cheaply obtained since it is very plentifully supplied by nature and is not used to any great extent in the arts. Other plants of a similar character might be employed for producing a material of this desired general character which will have some, if not all of the excellent qualities possessed by the material derived from eel grass.

In order to give a clearer understanding of the character of the product of the present invention we append hereto a drawing illustrating the use of our composite heat insulating material in connection with the steel wall panel of a railway car of steel construction, although it will be understood that the invention is not limited to the use for use, for

of the material in this particular connection.

In the drawing Figure 1 shows a side view of the steel wall with the insulating material applied thereto; Fig. 2 is a cross section taken on line 22 of Fig. 1.

Referring to .the drawing, A designates the steel panel and B the main body of the heat insulating sheet or board consisting of a stratum of closely felted vegetable fibers from which the non-fibrous elements of the plant have been removed to a very large extent. Integrally united with the stratum B is a facing C of vegetable matter which is much denser and tougher than the material making up the body B. If desired, the other surface of the stratum B may have a similar facing C. The composite board or sheet thus constituted may be secured to the steel panel A by cement, as indicated at D, or by means of any other suitable expedient. The character of the stratum B gives the sheet or board its heat insulating capacity. The strata or facings C, C are so dense in their character that they do not have a very high degree of insulating capaeity. Their purpose is to give the sheet tensile strength and stability and to provide a suitable facing for cementing or otherwise securing the sheet to the steel panel in connection with which the insulation is used. The material making up the stratum B is preferably produced as follows: The eel grass is boiled either at atmospheric pressure or under steam pressure in an alkaline solution, preferably a two per cent. solution of caustic soda, for a period of from one to siX hours, and the fibers of the plant are thereafter separated from the non-fibrous constituents, that is, pectic, resinous and nitrogenous matters, by washing and agitation. A portion of the fibrous matter subjected to the alkaline treatment just described is plunged in a dilute acid, for ex ample, a very dilute sulfuric acid, and kept suspended in the acid for a short time, say from five to fifteen minutes. The material is then washed, preferably by being suspended in a relatively large volume of water, to remove the non-cellular matter freed from the cellulose by the acid. This treat ment breaks down the fibers in a large measure, converting the material into a more or less gummy mass. Apparently the acid acts upon the cellulose by hydrolysis to convert the same into hydro-cellulose. The acid treated material is then mixed with a quantity of the fibers derived from the plant by the alkaline treatment above described. Preferably, we mix from thirty to fifty per cent. of the material from the acid treatment with from seventy to fifty per cent. of the cellulose which has been given only the alkaline treatment. This mixing may be done by suspending the ingredients in a large volume of water and agitating with compressed air or otherwise. The water is then drained off and the material rolled into a board or sheet. The product is avery close felt of uniform thickness and texture which is very pliable.

The facings C, C are preferably composed wholly of the hydro-cellulose produced by the acid treatment above described. The material is spread out upon the sheet D while both substances are wet and is integrally united therewith by pressure, for example by passing through rolls and drying. The density, toughness and homo geneous character of the material produced by the acid treatment is apparently due to the fact that this treatment hydrolyses the cellulose as above stated, and also removes therefrom the residue of pectic and nitrogenous matters separated out by the alkaline treatment, and furthermore, dissolves out certain mineral salts which the alkaline treatment does not afi'ect.

While we have described our invention in what .we consider the best exemplification thereof both as to the raw materials used and the methods of treating the same, it will be understood that modifications might be made without departure from the princiles of the invention.v While the product as a particular utility as a heat insulating material it might be used for other purposes in analogous situations. We do not claim herein broadly a material produced by treating the plant Zostem marina or other vegetable matter first with an alkali and then with an acid, nor the composition of matter produced by mixing this material with the fibers derived from the alkaline treatment, nor the methods involved in the production of said two substances, these inventions being described and claimed in our co-pending applications Serial No. 803,207 filed November 26, 1913, and Serial No. 803,208 filed. November 26, 1914:. In this application we seek to cover the composite sheet comprising the felt like stratum and the tougher, more tenacious stratum, as above described.

We claim 1. An insulating material comprising a stratum of felt-like vegetable fibers from which the non-fibrous constituents of the plants have been removed, and integrally united therewith a facing composed of fibrous material derived from like plants treated so as to make it denser and more tenacious than said felt'like stratum.

2. An insulating material comprising a stratum of felt-like cellulose fibers and integrally united therewith a facing of hydrocellulose.

3. An insulating material comprising a stratum of vegetable fibers and integrally united therewith a facing of material produced by treating like vegetable fibers with a dilute acid.

4. An insulating material comprising integrally united strata composed respectively of felted vegetable fibers and of a denser, more tenacious material produced from fibrous material by treating the same with an acid.

5. An insulating material comprising integrally united strata composed respectively pf felted cellulose fibers and of hydro-celluose.

6. An insulating material consisting of a unitary sheet comprising a stratum of vegetable fibers mixed with a substance produced by treating vegetable fibers with an acid, and a stratum made up entirely of said last named substance.

7. An insulating material consisting of a unitary sheet comprising a stratum of the felted fibers of the plant Zostem marina from which the non-fibrous constituents of the plant have been removed, and a stratum of material produced by treating the fibers of said plant with an acid.

8. An insulating material consisting of a unitary sheet comprising a stratum of the felted fibers of the plant Zostera marina from which the non-fibrous constituents of the plant have been removed, mixed with a substance produced from the fibers of said plant by treating the same with an acid, and a stratum consisting entirely of said last named substance.

9. An insulating material consisting of cellulose fibers derived from the plant Z0s tem marina, and a stratum of hydro-cellulose produced from the cellulose of said plant.

10. An insulating material consisting of cellulose fibers derived from the plant Zostam marina mixed with hydro-cellulose produced from the cellulose of said plant, and a stratum made up wholly of said last named substance.

HELON B. MACFARLAND. ROBERT J. SHOEMAKER.

Witnesses L. A. FALKENBERG, H. M. Gmnnsrna. 

